The present invention relates to the treatment of toxic waste contaminated sites which may contain chemical and/or radioactive compositions that pollute the environment and threaten public health and safety. The sites may contain one or more of various chemical and radioactive compositions, hydrocarbons and heavy metal contaminants. The contaminants present in such sites are wide ranging in both type and concentration levels. They vary from a wide range of organic, chlorinated and inorganic compounds and precious metals and in some cases such compounds may be mixed with radioactive materials ranging from low to intermediate radioactivity levels.
Conventional methods of remediating such waste disposal sites include:
1. Excavation and transportation of contaminated soils to other landfills; PA1 2. Excavation and transportation of contaminated soils to a central offsite treatment plant; PA1 3. Physical containment of the waste site with an impermeable wall which prevents migration of contaminants into the groundwater; PA1 4. In situ treatment of the contaminants by stripping volatile organic compounds therefrom without excavation; and PA1 5. In situ addition of treatment reagents without excavation.
Each of the above methods includes various drawbacks which primarily render them cost ineffective, dangerous to treatment personnel and generally ineffective treatment.
Operations which involve physical transportation of contaminated materials to a different treatment or landfill site clearly involve extra hazards of spill accidents during transport and the natural reluctance of residents in proximity to a landfill to accept additional materials which have been removed from other landfills or contaminated sites.
Prior art treatment methods which involve physical containment of a waste site with a contaminant barrier wall often result in a "bathtub effect" which often creates undesired downward migration or spillover of the contaminants through cracks or porosity of the containment wall.
In situ vapor extraction methods which involve the placement of standpipes into the contaminated subsurface for removal of volatiles inherently result in non-uniform treatment with the greatest effectiveness being only within a relatively short distance from the standpipes. Horizontal well systems are now believed to be somewhat more efficient although they are necessarily more difficult to install. U.S. Pat. No. 4,927,292 issued to Justice discloses such a system.
An in situ groundwater remediation system which uses two sets of horizontal wells at opposite sides of a generally unconfined contaminated zone, one for fluid injecting and one for extracting, is disclosed in U.S. Pat. No. 4,832,122 issued May 23, 1989 to Corey, et al.
Other methods which involve pumping and treatment of contaminated groundwater from an aquifer suffer from the problems of mass capital investment, high energy consumption and general inefficiency in treating the source of the problem, namely the contaminated soil.
It is therefore the primary object of the present invention to provide a cost effective and efficient method for in situ treatment of a hazardous waste disposal site.
In general, the solution to the problem involves conversion of the site into a self contained process reactor primarily through the use of a mobile apparatus comprising a trenching machine such as those disclosed in co-pending U.S. patent application Ser. No. 07/838,576 filed Feb. 18, 1992 by Frank E. Manchak, III and Peter Manchak which is capable of operating to subsurface depths as low as 40 feet below the ground elevation and which effectively excavates, processes, and immediately recirculates processed waste contaminated soil back into the excavated trench in a rapid and continuous fashion. The reactor is then operated by selectively causing volatilization of contaminants and moving them to a collection location in the reactor and selectively feeding selected treatment reagents and microorganisms thereto as desired.
Accordingly, the present invention provides